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- var utils = require('../utils')
- , nodes = require('../nodes');
- /**
- * Blend the `top` color over the `bottom`
- *
- * Examples:
- *
- * blend(rgba(#FFF, 0.5), #000)
- * // => #808080
- *
- * blend(rgba(#FFDE00,.42), #19C261)
- * // => #7ace38
- *
- * blend(rgba(lime, 0.5), rgba(red, 0.25))
- * // => rgba(128,128,0,0.625)
- *
- * @param {RGBA|HSLA} top
- * @param {RGBA|HSLA} [bottom=#fff]
- * @return {RGBA}
- * @api public
- */
- function blend(top, bottom){
- // TODO: different blend modes like overlay etc.
- utils.assertColor(top);
- top = top.rgba;
- bottom = bottom || new nodes.RGBA(255, 255, 255, 1);
- utils.assertColor(bottom);
- bottom = bottom.rgba;
- return new nodes.RGBA(
- top.r * top.a + bottom.r * (1 - top.a),
- top.g * top.a + bottom.g * (1 - top.a),
- top.b * top.a + bottom.b * (1 - top.a),
- top.a + bottom.a - top.a * bottom.a);
- };
- blend.params = ['top', 'bottom'];
- module.exports = blend;
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